NEW YORK (Reuters) - The United States has struck a deal with Pakistan to allow U.S. troops to hunt for al Qaeda leader Osama bin Laden this spring in an area of Pakistan where he is believed to be operating, the New Yorker magazine reported on Sunday.

Thousands of U.S. troops will be deployed in a tribal area of northwest Pakistan in return for Washington's support of President Pervez Musharraf's pardon of the Pakistani scientist who this month admitted leaking nuclear arms secrets to Iran, Libya and North Korea, investigative reporter Seymour Hersh wrote in the issue that goes on sale on Monday.

Full disclosure of Pakistani scientist Abdul Qadeer Khan's activities would have exposed him as "the worst nuclear-arms proliferator in the world," an intelligence official is quoted as saying.

"It's a quid pro quo," according to a former senior intelligence official. "We're going to get our troops inside Pakistan in return for not forcing Musharraf to deal with Khan."

Musharraf has also offered other help in the hunt for bin Laden, accused of masterminding the Sept. 11, 2001, attacks on the United States, according to the article.

"Musharraf told us, 'We've got guys inside. The people who provide fresh fruits and vegetables and herd the goats' for bin Laden and his al Qaeda followers," the intelligence official added.

The spring offensive could slow the tempo of U.S. operations in Iraq, the magazine said.

"It's going to be a full-court press," one Pentagon planner was quoted as saying. The article added that some of the most highly skilled U.S. Special Forces units would be shifted from Iraq to Pakistan.

Special Forces personnel have been briefed on their new assignments and in some cases have been given "warning orders" -- the stage before being sent into combat, according to a military adviser.